In vitro cultures of DRG
Individual lumbar DRG were dissected from E13.5 or E14.5 embryos and placed on Matrigel (BD Biosciences, San Jose, California, United States) coated coverslips in DMEM/F12 (Gibco, San Diego, California, United States), 2 mM L-Gln (Gibco), N2 (Gibco), and 1 mg/ml BSA (Sigma, St. Louis, Missouri, United States) without neurotrophins, or supplemented with either NGF (100 ng/ml, Gibco) or NT-3 (20 ng/ml, Sigma). DRG explants (n ≥ 20 for each condition) were cultured for 48 h, processed for immunocytochemistry, and analyzed using confocal microscopy.